1. Field of the Invention
The present invention relates to a lock assembly that has a generally cylindrical barrel into which either of a pair of substitutable plug-type operator assemblies can be inserted for rotation between at least a pair of angularly spaced positions to operate the lock, with at least one of the substitutable plug assemblies being key-operated and including key-operated tumblers for releasably locking the key-operated plug assembly in at least one of the angularly spaced positions, and with a releasable retainer mechanism permitting removal of an inserted plug assembly from the barrel only under controlled conditions. In preferred practice the lock assembly forms a component part of a "switch lock" (i.e., an electrical switch that normally is lock-operated). In preferred practice, the other of the substitutable plug assemblies includes a manually operable formation such as a knob, and, when inserted into the barrel in place of the key-operated plug assembly, permits the lock or switch lock to be operated without the need for a key.
2. Prior Art
Locks are known that have key-receivable plug-type operator assemblies that are retained within protectively enshrouding barrels, and that are operated in response to rotation of the plug assemblies relative to their associated barrels between at least a pair of angularly spaced positions. Likewise, switch locks are known that employ such locks coupled with electrical switch assemblies. Typically, a rear portion of a the barrel of a lock is rigidly connected to the housing of a rotary electrical switch, a rear portion of a key-receivable plug assembly is connected to a rotatable operator of the electrical switch, and switch operation is effected by rotating the plug assembly relative to the barrel between angularly spaced positions to effect corresponding rotation of the switch operator. Examples of switch locks of this general type are disclosed in such patents as U.S. Pat. Nos. 4,689,977, 4,633,689, 4,566,167, 4,427,852, 4,405,843 and 3,639,708 issued to Stanley C. Wolniak et al, referred to hereinafter as the "Switch Lock Patents," the disclosures of which are incorporated herein by reference.
The use of a U-shaped, spring-biased retaining member to fasten a key-receivable plug assembly within a surrounding barrel, with the retainer bridging complementary formations that are defined by the plug assembly and by the surrounding barrel is known. Features of a key-operable lock that employs such a spring-biased retaining mechanism are disclosed in U.S. Pat. No. 2,883,848 issued to Stanley C. Wolniak, referred to hereinafter as the "Permanently Assembled Lock Patent," the disclosure of which is incorporated herein by reference.
The use of a variety of groove-carried retention members that bridge from a groove that is formed in a portion of a key-receivable plug assembly to a complimentary groove that is formed in a surrounding portion of a barrel to fasten the plug assembly in the barrel is well known. In the above-referenced Permanently Assembled Lock Patent, such complementary grooves are provided near the rear end region of the plug assembly (i.e., complementary grooves carry a bridging retainer at a location that is spaced a substantial distance rearwardly from an enlarged diameter head formation that typically is provided near the front end region of the plug assembly). In some of the invention embodiments that are disclosed in the referenced Switch Lock Patents (e.g., in U.S. Pat. Nos. 4,566,167, 4,427,852 and 4,405,843), such complementary grooves are formed in peripheral surfaces of enlarged diameter head formations of the plug assemblies, and in surrounding barrel portions (i.e., complementary grooves carry retainers at locations that are near the front ends of the plug assemblies).
A variety of proposals have been made in efforts to provide relatively simple methods and/or means for permitting key-operable plug assemblies to be removed from the surrounding barrels of relatively high security locks and switch locks for maintenance and/or to enable the plug assemblies to be replaced with substitute plug assemblies. However, to the extent that it has been possible to carry out such proposals by accessing only the front-most portions of an installed high security lock or switch lock (i.e., by accessing only such portions of the installed lock or switch lock as normally are accessible), such proposals typically have required the use of are referred to as "control" keys (i.e., keys that differ in configuration from such "change" keys and "master" keys as may be used on a day-to-day basis to operate the locks and switch locks). In many instances, the need to configure the tumblers of relatively high security locks and switch locks to respond to the insertion of any of a plurality of differently configured keys results in a dramatic decrease in the resistance that the lock or switch lock offers to being picked, drilled, forced or otherwise defeated. Stated in another way, a drawback that is common to many prior proposals for modifying relatively high security locks and switch locks to enable their plug assemblies to be releasably retained within and removed from their associated barrels is that the implementation of these proposals has significantly diminished the level of security that otherwise would be provided by the locks and switch locks.
Various other proposals (i.e., proposals that do not utilize "control" keys and that arguably may not result in dramatic reductions of the level of security that otherwise is provided) have been advanced for enabling a skilled locksmith to remove key-receivable plug assemblies from the barrels of locks and switch locks once the locks and switch locks have been removed from their installation sites; however, these proposals, too, have tended to be characterized by drawbacks. Often, such proposals require the provision of a lock disassembly environment wherein a host of specially configured tools are readily at hand, such as is found in the shop of a locksmith. Some of the proposals call for the very precise drilling of one or more holes through sidewall portions of the barrel of a lock or switch lock to directly access components of the plug-retaining mechanism so that one or more components can be moved in ways that will defeat the operation of the plug-retaining mechanism and will thereby permit the plug assembly to be removed from its barrel.
Many of these "other proposals" are difficult if not impossible to implement on-site and without removing the entire lock or switch lock assembly from its installed position. Often, the environment of an installation does not afford needed room to adequately access external surfaces of the installed lock or key lock. Furthermore, proposals that involve drilling or the performing other operations on an installed lock or switch lock may be inappropriate for use at the site of an installed lock or switch lock inasmuch as they unacceptably risk damage to property and/or injury to personnel.
Thus, a need remains in on-site environments where locks and switch locks are installed for methods and means that can be utilized to safely, easily and nondestructively permit the removal, servicing and/or replacement of plug-type operator assemblies 1) without disturbing in any way the existing installation of the barrels of the locks and switch locks, 2) without requiring access to any parts of the locks and switch locks other than the front-most portions thereof that normally are accessible, 3) without causing the degree of security that is provided by the installed locks and switch locks to be diminished (once they have been reassembled), and 4) without doing anything that risks damage to the locks and switch locks, to the surrounding environment, or to personnel.
Still another need that is not addressed satisfactorily by prior proposals is encountered when equipment such as mainframe computer components are to be installed through the cooperative efforts of persons possessing a variety of needed skills, few if any of whom ought to be granted access to the key or keys that ultimately will be used to prevent unauthorized persons from accessing and operating the equipment. During installation (and also at other times during the service life of the equipment such as when the equipment is being moved to a new site), personnel who eventually should be excluded from being able to access the equipment need to be able to open normally lockable cabinets and to operate normally lock-controlled switches--whereby, there is a need for a simple method and means that permits the equipment's relatively high security plug assemblies to be removed (under controlled conditions) from the installed barrels of locks and switch locks, and to substitute relatively low security plug assemblies and/ or manually operable plug assemblies in place of selected ones of the high security key-operated plug assemblies. By such an arrangement, undesired access to equipment-operating keys can be denied to those who should not have such access while, at the same time, permitting such activities as installation, servicing and moving of the equipment to proceed unhindered by the absence of normally required equipment-operating keys.
The extent to which a particular lock or switch lock is deemed to be "secure" depends to a significant degree on the character of the locking mechanism and its key, and on how the locking mechanism functions. Locks and switch locks are known that offer relatively high security by using complexly configured, precision formed keys to operate relatively large numbers of plug-carried tumblers that must be correctly positioned simultaneously in order to permit plug-type operator assemblies to be rotated relative to surrounding barrels between pairs of angularly spaced positions. Locks and switch locks of this type are exemplified by those that are sold by The Illinois Lock Company division of The Eastern Company and that have keys that bear the registered trademark DUO.
Double-bitted key-operated locks such as DUO locks have been commercially available for many years. However, because the best mode known to the inventors for carrying out the preferred practice of the present invention involves utilizing of selected features of DUO locks to enhance the security of the resulting lock and switch lock products, a brief overview of relevant features of typical DUO lock components is included here.
One feature of a DUO key is that it actually has three "cuts" or "serratures," namely two "primary" serratures and a "secondary" serrature. The primary serratures give the key its "double bitted" character in that the primary serratures are defined by opposed wavy outer edge formations that are cut into opposed edge portions of a pair of flanges that extend in opposite directions from a relatively thicker, grooved, elongate central region of the body of the key. The primary serratures are among the most notable features of the body of a DUO key (i.e., the primary serratures define the width of the body along the majority of the length of the body, and therefore constitute prominent elements of the appearance of a DUO brand key). In contradistinction, the secondary serrature is a "single bitted" cut that extends relatively inconspicuously along one surface of the relatively thick central region.
While the secondary serrature is independently configured (i.e., its configuration is not dictated by the configuration of either of the primary serratures), the configurations of the primary serratures are interdependent in the sense that they are "oppositely coordinated." As one edge of the body portion of a DUO key curves away from the central region (due to the shape of one of the primary serratures), the corresponding opposite edge of the body portion curves inwardly toward the central region (due to the "oppositely coordinated" shape of the other of the primary serratures). One effect that results from the way in which the configurations of the primary serratures are "oppositely coordinated" is that the width of the body (i.e., the distance between the opposed primary serratures as measured transversely relative to the grooved central region of the body of the key) is maintained relatively constant along a majority of its length.
The key is insertable along a keyway that opens through the front end of a plug assembly and parallels a central axis that extends through the plug-receiving chamber of the barrel. A tumbler positioning compartment having opposed side walls that extend along on opposite sides of the keyway is formed in the body of the plug. A front end wall of the tumbler compartment is located just behind the enlarged diameter head formation that is defined by the front end region of the body of the plug. A rear end wall of the tumbler compartment typically is spaced along the central axis half an inch or more rearwardly from the front end wall, whereby space is provided within the tumbler compartment to hold a substantial number of wafer-like members that are arranged side-by-side so as to extend in parallel planes that are transverse relative to the keyway and relative to the central axis. The opposed side walls that extend forwardly and rearwardly between the front and rear end walls carry a series of shallow groove formations or splines that help to guide and position the wafer-like contents of the tumbler compartment.
Beginning at the front end wall of the tumbler compartment and extending rearwardly, the contents of the tumbler compartment typically comprise a number of wafer-like components including what can be through of as "sets" of wafer tumblers that are separated by wafer-like key guides. When a double-bitted key is inserted along the keyway, the oppositely coordinated primary serratures of the key pass through precisely configured holes (i.e., "piercings") that are formed through the tumblers and through the key guides; and, at the same time, the secondary serrature also moves through these same piercings. Because a close "working clearance" is provided between the opposed primary serratures and opposed ends of the tumbler piercings, movement of the key along the keyway will cause the tumblers to be moved transversely relative to the keyway in a positive fashion that does not rely on any external force (e.g., gravity, spring biasing force, etc.) to assure that the tumblers are moved to positions that correspond to the configurations of the key serratures.
The key guides emulate the cross-section of portions of an appropriately configured key so as to guide the key for smooth movement along the keyway and through the piercings of the tumblers. The key guides do not move transversely relative to the keyway; rather, they remain stationary once inserted into a splined central section of the body. The key guides cooperate with a machined opening that is formed in the enlarged diameter head of the body of the plug to assist in guiding a properly configured key into and out of an unlocking position. When a properly configured key is fully inserted into a plug assembly to its "unlocking" position, the engagements made by end regions of the tumbler piercings with the serratures of the key cause the tumblers to align with peripheral portions of the generally cylindrical body of the plug to permit the plug to rotate about the central axis relative to the surrounding barrel.
So that end portions of the tumblers of a DUO lock will tend to project radially outwardly with respect to the generally cylindrical plug body when no correctly configured key is inserted into the keyway, compression coil springs are provided, with each tumbler being biased radially outwardly with respect to the plug body by virtue of its being engaged by a separate spring end region. Some pairs of adjacent tumblers of a DUO lock typically are biased in opposite directions by compression coil springs that are interposed between the adjacent tumblers. Others of the tumblers (typically some that reside adjacent the key guides) are biased outwardly by springs that engage the key guides.
DUO locks typically utilize 1) opposed pairs of "primary" tumblers that are positioned by the "oppositely coordinated" key serratures that are referred to by the term "primary," and 2) an interspersed array of "secondary" tumblers that are positioned by the independently configured key serrature that is referred to by the term "secondary." In a DUO lock, typically about every third tumbler that is positioned along the keyway is a secondary tumbler. The most common arrangement of wafer-like components in the tumbler compartment of a DUO plug body includes four components, namely three tumblers and one key guide. Typically, such four-component sets include a pair of adjacent, opposed primary tumblers (i.e., they project from opposed sides of the generally cylindrical body of the plug into opposed spline formations that are defined within the interior of the surrounding barrel), a secondary tumbler (since it rides on a single bitted serrature, all of the secondary tumblers tend to project from the body of the plug into a single one of the opposed spline formations of the barrel), and a key guide. Usually, the secondary tumbler is sandwiched between the key guide and one of the primary tumblers. Four-component sets of this nature are arranged one after another extending from the front end wall of the tumbler compartment toward the rear end wall. A typical DUO lock has four such sets followed by "added" wafer-like components that typically include at least a pair of "added" opposed primary tumblers, perhaps an "added" secondary tumbler and an "added" key guide, with empty positions typically being filled by "dummy" tumblers that serve principally to assist in maintaining the "added" components in proper locations within the tumbler compartment.
In operation, when no properly configured key is in an operating position along the keyway of a DUO lock, end regions of the tumblers project from opposite sides of the body of the plug for extension into splined recesses that are defined by the interior configuration of the barrel that surrounds and protectively enshrouds all but a forward end portion of the plug through which the keyway opens. However, insertion of a properly configured key along the keyway to its unlocking position causes the tumbler ends to align with peripheral portions of the body of the plug, whereby the plug is permitted to rotate between at least a pair of angularly spaced positions.